This disclosure relates to composite articles such as those used in gas turbine engines.
Components, such as gas turbine engine components, may be subjected to high temperatures, corrosive and oxidative conditions, and elevated stress levels. In order to improve the thermal and oxidative stability of these components, the component may include a protective layer such as an environmental barrier, a thermal barrier or a velocity barrier coating or a coating that is selectively abradable or resistant to erosion. The barrier coating may be a multi-layer coating that includes a top coat and a bond coat beneath the top coat to adhere the top coat to the underlying substrate.